Hydrogen storage system materials and methods including hydrides and hydroxides

ABSTRACT

In one aspect, the present invention provides a system for methods of producing and releasing hydrogen from hydrogen storage compositions having a hydrogenated state and a dehydrogenated state. In the hydrogenated state, such a composition comprises a hydride and a hydroxide. In a dehydrogenated state, the composition comprises an oxide. A first reaction is conducted between a portion of the hydride and water to generate heat sufficient to cause a second hydrogen production reaction between a remaining portion of the hydride and the hydroxide.

FIELD OF THE INVENTION

The present invention relates to hydrogen storage compositions, themethod of making such hydrogen storage compositions and use thereof.

BACKGROUND OF THE INVENTION

Hydrogen is desirable as a source of energy because it reacts cleanlywith air producing water as a by-product. In order to enhance thedesirability of hydrogen as a fuel source, particularly for mobileapplications, it is desirable to increase the available energy contentper unit volume and per unit mass of storage. Presently, this is done byconventional means such as storage under high pressure, at thousands ofpounds per square inch (e.g., 5,000 to 10,000 psi), cooling to a liquidstate, or absorbing into a solid such as a metal hydride. Pressurizationand liquification require relatively expensive processing and storageequipment.

Storing hydrogen in a solid material such as metal hydrides, providesvolumetric hydrogen density which is relatively high and compact as astorage medium. Binding the hydrogen as a solid is desirable since itdesorbs when heat is applied, thereby providing a controllable source ofhydrogen.

Rechargeable hydrogen storage devices have been proposed to facilitatethe use of hydrogen. Such devices may be relatively simple and generallyare simply constructed as a shell and tube heat exchanger where the heattransfer medium delivers heat for desorption. Such heat transfer mediumis supplied in channels separate from the chamber which houses thehydrogen storage material. Therefore, when hydrogen release is desired,fluids at different temperatures may be circulated through the channels,in heat transfer relationship with the storage material, to facilitaterelease of the hydrogen. For certain materials, recharging the storagemedium can be achieved by pumping hydrogen into the chamber and throughthe storage material while the heat transfer medium removes heat, thusfacilitating the charging or hydrogenating process. An exemplaryhydrogen storage material and storage device arranged to providesuitable heat transfer surface and heat transfer medium for temperaturemanagement is exemplified in U.S. Pat. No. 6,015,041.

Presently, the selection of relatively light weight hydrogen storagematerial is essentially limited to magnesium and magnesium-based alloyswhich provide hydrogen storage capacity of several weight percent,essentially the best known conventional storage material with somereversible performance. However, such magnesium based materials have alimitation in that they take up hydrogen at very high temperature andhigh hydrogen pressure. In addition, hydrogenation of the storagematerial is typically impeded by surface oxidation of the magnesium.Other examples, such as LaNi₅ and TiFe, have relatively low gravimetrichydrogen storage density, since they are very heavy.

Therefore, in response to the desire for an improved hydrogen storagemedium, the present invention provides an improved hydrogen storagecomposition, its use as a storage medium and a method for forming suchmaterials.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a method of producing hydrogencomprising reacting a first portion of a hydride with water to produceheat and causing a second reaction between a second portion of thehydride and a hydroxide, by transferring the heat thereto.

In another aspect, the invention provides a method of producing hydrogencomprising: generating heat in a first reaction by reacting water with aportion of a hydride present in a first material composition, whereinthe heat is used in a hydrogen production reaction. A remaining portionof the hydride present in the first material composition is reacted witha hydroxide present in a second material composition in the hydrogenproduction reaction, thereby forming a hydrogen product and a byproductcomposition comprising an oxide.

In still another aspect of the invention, there is provided a hydrogenstorage composition having a hydrogenated state and a dehydrogenatedstate: where in the hydrogenated state, the composition comprises ahydride and a hydrated hydroxide; and in the dehydrogenated state, thecomposition comprises an oxide.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 shows hydrogen production by weight percent loss of hydrogen froma hydrogen storage material comprising lithium hydride and lithiumhydroxide analyzed by a modified volumetric Sievert's apparatusanalysis;

FIG. 2 is a graph showing hydrogen production for a hydrogen storagematerial comparing a first sample comprising lithium hydride and lithiumhydroxide and a second sample comprising lithium hydride, lithiumhydroxide, and a catalyst, where temperature is incrementally increasedin a modified Sievert's apparatus;

FIG. 3 is a graph showing hydrogen production over time for a hydrogenstorage material comprising sodium hydride and lithium hydroxide from amodified Sievert's apparatus analysis; and

FIG. 4 is a graph showing hydrogen production over time for a hydrogenstorage material comprising a complex hydride of lithium boroydride andlithium hydroxide from a modified Sievert's apparatus analysis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

In one aspect, the present invention provides a system for producing andreleasing hydrogen from a hydrogen storage material system. In onepreferred embodiment, a method is provided for releasing hydrogen fromhydrogen storage materials by conducting a first reaction between afirst portion of a hydride composition and water. This first reactiongenerates heat, which is used to initiate a second hydrogen productionreaction. The hydrogen production reaction is conducted by reacting ahydride composition and a hydroxide composition. The hydrogen productionreaction produces hydrogen and a reaction byproduct comprising an oxidecomposition. As used herein, the term “composition” refers broadly to asubstance containing at least the preferred chemical compound, but whichmay also comprise additional substances or compounds, includingimpurities. The term “material” also broadly refers to matter containingthe preferred compound or composition. Other preferred embodiments ofthe present invention relate to methods of releasing hydrogen fromhydrogen storage compositions, as will be discussed in greater detailbelow.

In another aspect, the present invention provides hydrogen storagematerials. In one preferred embodiment of the present invention, ahydrogen storage composition has a hydrogenated state and adehydrogenated state, therein providing two distinct physical stateswhere hydrogen can be stored and subsequently released. In thehydrogenated state, the composition comprises a hydride and a hydroxide.In the dehydrogenated state, the composition comprises an oxide. Thehydrated hydroxide compound reacts with a portion of the hydride togenerate heat sufficient to initiate a dehydrogenation reactionresulting in the dehydrogenated product.

In one preferred embodiment of the present invention, the hydride isrepresented by the general formula MI^(x)H_(x), where MI represents oneor more cationic species other than hydrogen, and x represents theaverage valence state of MI, where the average valence state maintainsthe charge neutrality of the compound.

In another preferred embodiment of the present invention, the hydroxideis represented by the general formula MII^(y)(OH)_(y), where MIIrepresents one or more cationic species other than hydrogen, and yrepresents the average valence state of MII where the average valencestate maintains the charge neutrality of the compound.

In yet another preferred embodiment of the present invention, thehydride composition is represented by MI^(x)H_(x) and the hydroxidecomposition is represented by MII^(y)(OH)_(y), where MI and MIIrespectively represent one or more cationic species other than hydrogen,and x and y represent average valence states of MI and MII, and wherethe average valence states maintain the charge neutrality of thecompounds, respectively.

In accordance with the present invention, MI and MII each represent oneor more of a cationic species or a mixture of cationic species otherthan hydrogen. It should be noted that MI and MII are independentlyselected from one another. Thus, the present invention contemplates MIand MII comprising the same cationic species, or in alternate preferredembodiments, MI and MII comprise distinct cationic species that aredifferent from one another. Further, MI, MII, or both may be selected tobe complex cations, which comprise two or more distinct cationicspecies. In the case where MI, MII, or both are complex cations, MI andMII may comprise one or more of the same cationic species, or may haveentirely distinct cationic species from one another. Hydrides are oftenreferred to as complex hydrides, which are further contemplated in thepresent invention. A complex hydride comprises two cationic species,however one of the cationic species forms an anionic group withhydrogen, which further interacts with a second cationic species. Thisconcept can be expressed by the following formula with a hydrideexpressed as MI^(x)H^(x), where MI comprises two distinct cationicspecies, M′ and M″, so that MI=M′+M″. Thus, the hydride can be expressedas: M′_(d) ^(a)(M″^(b)H_(c))_(a) ^(−d) where (M″^(b)H_(c)) is an anionicgroup, where d=(c−b) and a, b, c, and d are selected so as to maintaincharge balance and electroneutrality of the compound. Cationic speciesthat are preferred for all the preferred embodiments of the presentinvention include metal cations, as well as non-metal cations such asboron. Further, MII is also optionally selected to be an organiccationic group non-metal cation, such as CH₃.

Elements that form preferred cations and mixtures of cations for MI andMII in the type of compounds of the present invention are as follows.For both hydrides and hydroxides, certain preferred cationic speciescomprise: aluminum (Al), boron (B), barium (Ba), beryllium (Be), calcium(Ca), cesium (Cs), potassium (K), lithium (Li), magnesium (Mg), sodium(Na), rubidium (Rb), silicon (Si), strontium (Sr), titanium (Ti),vanadium (V), and mixtures thereof. Particularly preferred elementscomprise: aluminum (Al), boron (B), beryllium (Be), calcium (Ca),potassium (K), lithium (Li), magnesium (Mg), sodium (Na), strontium(Sr), titanium (Ti), and mixtures thereof. The most preferred cationicspecies are Li and Na. Evaluation of the aforesaid known speciesproduces, by analogy, the following added cationic species besides thoserecited above which are thought to be usable based on predictivethermodynamics, but not yet demonstrated, include arsenic (As), cadmium(Cd), cerium (Ce), europium (Eu), iron (Fe), gallium (Ga), gadolinium(Gd), germanium (Ge), hafnium (Hf), mercury (Hg), indium (In), lanthanum(La), manganese (Mn), neodymium (Nd), nickel (Ni), lead (Pb),praseodymium (Pr), antimony (Sb), scandium (Sc), selenium (Se), samarium(Sm), tin (Sn), thorium (Th), thallium (TI), tungsten (W), yttrium (Y),ytterbium (Yb), zinc (Zn), zirconium (Zr). For MII, another feasiblecationic species comprises low molecular weight organic groups, such asmethyl (CH₃), ethyl (C₂H₅), and propyl (C₃H₇) groups.

In view of the above, the cationic species MI or MII generally comprise:aluminum (Al), arsenic (As), boron (B), barium (Ba), beryllium (Be),calcium (Ca), cadmium (Cd), cerium (Ce), cesium (Cs), copper (Cu),europium (Eu), iron (Fe), gallium (Ga), gadolinium (Gd), germanium (Ge),hafnium (Hf), mercury (Hg), indium (In), potassium (K), lanthanum (La),lithium (Li), magnesium (Mg), manganese (Mn), sodium (Na), neodymium(Nd), nickel (Ni), lead (Pb), praseodymium (Pr), rubidium (Rb), antimony(Sb), scandium (Sc), selenium (Se), silicon (Si), samarium (Sm), tin(Sn), strontium (Sr), thorium (Th), titanium (Ti), thallium (TI),tungsten (W), yttrium (Y), ytterbium (Yb), zinc (Zn), and zirconium(Zr). Additionally, MII may comprise an organic cationic species, suchas methyl (CH₃), ethyl (C₂H₅), and propyl (C₃H₇) groups.

In preferred embodiments of the present invention, a solid-state hydridecomposition (i.e., in particulate form) reacts with a hydroxidecomposition (i.e., in particulate form) via a solid-state reaction toproduce and release gaseous hydrogen and a solid-state byproductcompound comprising an oxide. Where the hydride composition is selectedas MI^(x)H^(x) and the hydroxide composition is selected asMII^(y)(OH)_(y), the hydrogen production reaction proceeds by thefollowing reaction mechanism:${{{yMI}^{X}H_{x}} + {{xMII}^{y}({OH})}_{y}}->{{{xy}H}_{2} + {\left( \frac{xy}{2} \right){MI}_{(\frac{2}{x})}O} + {\left( \frac{xy}{2} \right){MII}_{(\frac{2}{y})}O}}$where as previously discussed, x is the average valence state of MI andy is the average valence state of MII where the average valence statesmaintain the charge neutrality of the respective compounds. Thus, thehydrogenated state of the hydrogen storage composition corresponds tothe hydrogenated hydride and hydrogenated hydroxide, and thedehydrogenated hydrogen storage composition corresponds to the one ormore byproduct compounds comprising an oxide. It should be noted thatwhere MI and MII are the same cationic species, which can be representedby M, the above reaction mechanism can be simplified to:${{M^{z}H_{z}} + {M^{\quad z}({OH})}_{z}}->{{zH}_{2} + {{zM}_{(\frac{2}{z})}O}}$where z represents the average valence state of M, where the averagevalence state maintains the charge neutrality of the compound.

According to the present invention, it is preferred that at least onebyproduct composition comprises an oxide having one or more cationicspecies of the hydroxide and hydride (i.e., MI, MII, or both). Theindependent selection of cationic species can vary the stoichiometry ofthe reaction and the types of byproduct compounds formed. It should benoted that the oxide byproduct compounds${MI}_{\frac{2}{x}}O\quad{and}\quad{MII}_{\frac{2}{y}}O\quad\left( {{or}\quad M_{\frac{2}{z}}O} \right.$in the case where MI and MII are the same cation M) maythermodynamically favor forming and/or decomposing into differentbyproduct compounds. Further, with certain reactants and stoichiometryof the reactants, such oxide byproduct compounds may also comprisehigher-order complex hydrides, for example, as will be described in moredetail below. These further byproducts are formed of the same generalconstituents as the primary byproducts, but they have different valencestates, atomic ratios, or stoichiometry, depending on the cationicspecies involved, as recognized by one of skill in the art.

In certain preferred embodiments of the present invention the hydrogenstorage composition comprises a hydride selected from the groupconsisting of: lithium hydride (LiH), sodium hydride (NaH), potassiumhydride (KH), beryllium hydride (BeH₂), magnesium hydride (MgH₂),calcium hydride (CaH₂), strontium hydride (SrH₂), titanium hydride(TiH₂), aluminum hydride (AlH₃), boron hydride (BH₃), and mixturesthereof. Particularly preferred hydride compositions comprise LiH orNaH.

In alternate preferred embodiments of the present invention the hydrogenstorage composition comprises a hydride which is a complex hydrideselected from the group consisting of: lithium borohydride (LiBH₄),sodium borohydride (NaBH₄), magnesium borohydride (Mg(BH₄)₂), calciumborohydride (Ca(BH₄)₂), lithium alanate (LiAlH₄), sodium alanate(NaAlH₄), magnesium alanate (Mg(AlH₄)₂), calcium alanate (Ca(AlH₄)₂),and mixtures thereof. Particularly preferred complex hydrides compriselithium borohydride (LiBH₄), sodium borohydride (NaBH₄), lithium alanate(LiAlH₄), and sodium alanate (NaAlH₄).

Further, other preferred embodiments of the present invention, comprisea hydroxide composition selected from the group consisting of: lithiumhydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH),beryllium hydroxide (Be(OH)₂), magnesium hydroxide (Mg(OH)₂), calciumhydroxide (Ca(OH)₂), strontium hydroxide (Sr(OH)₂), titanium hydroxide(Ti(OH)₂), aluminum hydroxide (Al(OH)₃), boron hydroxide (B(OH)₃) whichis also known as boric acid and more conventionally is expressed as(H₃BO₃), and mixtures thereof. Particularly preferred hydroxidecompounds comprise LiOH and NaOH.

Thus, according to one preferred embodiment of the present invention, ahydrogen production reaction is conducted by reacting a hydridecomprising LiH with a hydroxide comprising LiOH. The reaction proceedsaccording to the reaction mechanism:LiH+LiOH→Li₂O+H₂.This reaction produces a theoretical 6.25 weight % of hydrogen on amaterial basis.

In an alternate preferred embodiment of the present invention a hydrogenproduction reaction occurs by reacting a hydride comprising NaH with ahydroxide comprising LiOH. The reaction mechanism for this reaction canbe expressed asNaH+LiOH→½Li₂O+½Na₂O+H₂.This reaction generates a theoretical 4.1 weight % hydrogen on amaterial basis. It should be noted that the byproduct compounds aregenerally expressed as Li₂O and Na₂O, however, mixed or partially mixedmetal oxides may form based on the conditions at which the reactiontakes place, and may be thermodynamically favored. Thus, for example,the byproduct composition may comprise an oxide composition comprising amixed cation oxide$\left( {{MI}^{x}{MII}_{\frac{2}{x + y}}^{y}O} \right)$formed as a byproduct, where x and y are the average valence states ofMI and MII, respectively, and where the average valence state maintainsthe charge neutrality of the compound. In such a case, the abovereaction may form LiNaO as a byproduct compound. The mixed cation oxidebyproduct compound may comprise the entire oxide product, or may bemixed with the single cation oxides to result in multiple distinct oxidebyproduct compounds, depending on the thermodynamics of the reaction.

In certain preferred embodiments of the present invention, the reactionmechanism for producing hydrogen from the hydride and hydroxide isreversible. By “reversible” it is meant that a species of a startingmaterial hydroxide or hydride is regenerated at temperature and pressureconditions which are economically and industrially useful andpracticable. Particularly preferred “reversible” reactions include thosewhere exposing one or more byproduct compounds to hydrogen regenerates aspecies of a starting material hydroxide or hydride. In the same manner,a “non-reversible reaction” generally applies to both reactions that areirreversible via the reaction mechanism pathway, and also to thosereactions where regenerating a species of a starting material hydride orhydroxide by exposure to hydrogen is carried out at impracticalprocessing conditions, such as, extreme temperature, extreme pressure,or cumbersome product removal, which prevents its widespread andpractical use. Endothermic hydrogen formation reactions according to thepresent invention are generally reversible at desirable temperature andpressure conditions.

One aspect of the present invention is a reduction in the overall energyrequirements for a system of storing and subsequently releasinghydrogen. Minimizing the overall enthalpy changes associated with thehydrogen storage material system results in an improvement of theoverall efficiency of the fuel cell system. As the overall enthalpychange increases, so do the requirements for managing heat transfersystems (heating and cooling operations). In particular, it is highlyadvantageous to minimize heating and cooling systems in mobile unitscontaining fuel cells (e.g., vehicles or electronic devices), becauseadditional systems draw parasitic energy and increase the overall weightof the mobile unit, thereby decreasing its gravimetric efficiency.

Other advantages of minimizing overall enthalpy change in the hydrogenstorage system are often realized during start-up and other transientconditions (e.g., low load conditions), because there is less diversionof energy from other important system operations. Thus, one aspect ofthe present invention is a minimization of the overall energy necessaryto both produce and regenerate a hydrogen storage material. In preferredembodiments of the present invention, the energy required for hydrogenproduction and recharge is relatively low, and vastly improved whencompared to energy requirements of prior art hydrogen storage systems.

As previously discussed, one preferred embodiment of the presentinvention comprises a hydrogen storage composition where the hydride islithium hydride LiH and the hydroxide is lithium hydroxide LiOH, whichreact with one another to form Li₂O and H₂. The enthalpy of reaction(ΔH_(r)) for the hydrogen production reaction was calculated based onthe standard heat of formation (ΔH_(r)) for each of the compounds, andresulted in theoretical ΔH_(r) of −23.3 kJ/mol-H₂. This ΔH_(r) indicatesan exothermic reaction, with a relatively low enthalpy (and thus a lowlevel of heat production). Minimizing the amount of heat released intothe fuel cell system is preferred, because larger enthalpies result inlarger quantities of emitted heat, which must be controlled by coolingsystems to prevent damage to the surrounding environment, especially ina fuel cell system where certain components (e.g., control circuitry orthe membrane exchange assembly (MEA)) potentially degrade upon exposureto higher temperatures. As the enthalpy of the reaction increases, thesize and complexity of the heat transfer system becomes much larger.Further, larger heats of reaction have the potential to be lesscontrollable and often cannot be stopped prior to complete reaction. Thepresent embodiment thus provides a relatively low exothermic heat ofreaction for the hydrogen production reaction. An exothermic hydrogenproduction reaction has an advantage of not requiring a sustained inputof external energy from the fuel cell system for hydrogen generation(aside from any activation energy necessary to initiate the reaction, aswill be discussed in more detail below). It is preferred that the heatreleased by the hydrogen generation reaction is dissipated by a heattransfer system, as it is preferred to maintain the storage materials ata constant temperature during the reaction. However, the presentembodiment does not require an extensive cooling system and furtherprovides good control over the reaction as it proceeds.

Other preferred embodiments according to the present invention have anexothermic hydrogen production reaction and include reactions between ahydride composition MI^(x)H^(x) and a hydroxide compositionMII^(y)(OH)_(y), where MI and MII are selected to be the same cationicspecies selected from the group consisting of Al, B, Be, Ca, Mg, Sr, andTi. These reactions have a higher enthalpy of reaction ΔH_(r) than theprevious embodiment, and include for example, the following reactions.Where the hydride is selected to be MgH₂ and the hydroxide is selectedto be Mg(OH)₂, the reaction can be expressed as:MgH₂+Mg(OH)₂→MgO+2H₂

-   -   which has a ΔH_(r) of −101.3 kJ/mol-H₂ and a theoretical        hydrogen production of 4.7 wt. %. Where the hydride is selected        to be AlH₃ and the hydroxide is selected to be Al(OH)₃, the        reaction can be expressed as:        AlH₃+Al(OH)₃→Al₂O₃+3H₂    -   which has a ΔH_(r) of −129.3 kJ/mol-H₂ and a theoretical        hydrogen production of 5.5 wt. %. In the case where the hydride        is selected to be CaH₂ and the hydroxide is selected to be        Ca(OH)₂, the reaction can be expressed as:        CaH₂+Ca(OH)₂→CaO+2H₂    -   which has a ΔH_(r) of −53.7 kJ/mol-H₂ and a theoretical hydrogen        production of 3.4 wt. %. Where the hydride is selected to be        SrH₂ and the hydroxide is selected to be Sr(OH)₂, the reaction        can be expressed as:        SrH₂+Sr(OH)₂→SrO+2H₂    -   which has a ΔH_(r) of −17.7 kJ/mol-H₂ and a theoretical hydrogen        production of 1.9 wt. %. Where the hydride is selected to be BH₃        and the hydroxide is selected to be B(OH)₃, the reaction can be        expressed as:        BH₃+B(OH)₃→B₂O₃+3H₂    -   which has a ΔH_(r) of −94.9 kJ/mol-H₂ and a theoretical hydrogen        production of 7.9 wt. %. Where the hydride is selected to be        BeH₂ and the hydroxide is selected to be Be(OH)₂, the reaction        can be expressed as:        BeH₂+Be(OH)₂→BeO+2H₂        which has a ΔH_(r) of −147.4 kJ/mol-H₂ and a theoretical        hydrogen production of 7.4 wt. %.

An additional exothermic hydrogen production reaction according to thepresent invention comprises reacting lithium hydride (LiH) with boronhydroxide (B(OH)₃) (which is more typically known as boric acid andexpressed as H₃BO₃), which under certain pressure, temperature, andother reaction conditions proceeds by the following reaction mechanism:3LiH+H₃BO₃→LiBO₂+Li₂O+3H₂which has a ΔH_(r) of −84.2 kJ/mol-H₂ and a theoretical hydrogenproduction of 6.9 wt. %. Under different pressure, temperature, andother reaction conditions, the same reactants can proceed according tothe following reaction mechanism, where the oxide product differs fromthe two oxide products above(i.e., LiBO₂ and Li₂O), and forms a singlecomplex higher order oxide product (Li₃BO₃):3LiH+H₃BO₃→Li₃BO₃+3H₂which likewise has a ΔH_(r) of −84.2 kJ/mol-H₂ and a theoreticalhydrogen production of 6.9 wt. %.

Further preferred alternate embodiments of the present invention, arewhere the hydride composition is MI^(x)H^(x) and the hydroxide isMII^(y)(OH)_(y), where the hydride is a complex hydride M′_(d)^(a)(M″^(b)H_(c))^(−d) where M′ is selected to be lithium and M″ isselected to be boron, and the reaction is exothermic, include thefollowing reactions. The first hydrogen production reaction occursbetween:LiBH₄+4 LiOH→LiBO₂+2 Li₂O+4H₂where a theoretical 6.8 weight % of hydrogen is produced and thereaction has a ΔH_(r) of −22 kJ/mol-H₂. A second hydrogen productionreaction with a complex hydride where M′ is sodium and M″ is boron,includes the reaction:NaBH₄+2 Mg(OH)₂→NaBO₂+2MgO+4H₂which produces a theoretical 5.2 weight % of hydrogen and a ΔH_(r) of−34 kJ/mol-H₂.

Another preferred embodiment of the present invention previouslydiscussed is that where the hydride is sodium hydride (NaH) and thehydroxide is lithium hydroxide (LiOH). A calculated heat of reaction(ΔH_(r)) is +9.7 kJ/mol-H₂, which indicates an endothermic heat ofreaction, which is relatively small. Thus, producing hydrogen with thishydrogen storage material system would require only slight heatingthroughout the hydrogen production reaction. However, because theoverall quantity of heat generated is relatively low, this embodiment ispreferred for certain applications. The endothermic nature of thehydrogen production reaction allows for an exothermic rechargingreaction.

In certain applications, this hydrogen storage material composition maybe preferred because the regeneration reaction is generally reversibleat relatively low temperature and pressure conditions. For example, apredicted equilibrium pressure for the byproduct material comprisingoxide is approximately 1 bar at 50° C., thus upon exposure topressurized hydrogen above the equilibrium pressure, the material willabsorb and react with hydrogen to regenerate a species of the hydrideand hydroxide: NaH and LiOH (and preferably both). It should be notedthat in circumstances where the byproduct composition comprises a mixedcation oxide (LiNaO), the species of regenerated hydride and hydroxidesmay also comprise a species of hydride and hydroxide different from thestarting material compositions, for example NaOH, LiH, or mixed cationhydrides and hydroxides, such as LiNa(OH)₂, for example. As recognizedby one of skill in the art, when the materials are recharged to formdifferent starting materials comprising a species of hydroxide andhydride, the hydrogen production reaction thermodynamics may change,such that the heat of reaction may likewise changes. The feasibility ofrecharging the hydrogen storage material with hydrogen at relatively lowtemperatures and pressures makes the present embodiment, and those withsimilar properties, desirable for mobile units, where the hydrogenstorage material can be regenerated at the point-of-use (e.g.,on-board), without need for further processing and reacting at anoffsite facility.

Other preferred embodiments according to the present invention, wherethe hydrogen generation reaction is endothermic, include one where MIand MII are each selected to be sodium, such that the hydrogenproduction reaction proceeds according to the reaction mechanism:NaH+NaOH→Na₂O+H₂,that has a theoretical hydrogen production amount of 3.1 weight %. Thetheoretical enthalpy of reaction ΔH_(r) is +67.4 kJ/mol-H₂. The presentembodiment is likewise useful for on-board regeneration for a mobileunit, and has a predicted equilibrium pressure of 1 bar at 475° C.Another preferred embodiment is where MI and MII are selected to bepotassium, and proceeds according to the reaction mechanism:KH+KOH→K₂O+H₂with a theoretical hydrogen generation of 2.1 weight %. The theoreticalenthalpy of reaction ΔH_(r) for the potassium hydroxide and potassiumhydride hydrogen production reaction is +119.7 kJ/mol-H₂.

Further preferred alternate embodiments of the present invention, wherethe hydrogen production reaction is exothermic are where the hydridecomposition is MI^(x)H^(x) and the hydroxide is MII^(y)(OH)_(y), wherethe hydride is selected to be a complex hydride (i.e., M′_(d)^(a)(M′_(b)H_(c))^(−d), for example, NaBH₄, where M′ is Na and M″ is B)and the reaction is endothermic, include the following exemplaryreaction:NaBH₄+4NaOH→NaBO₂+2Na₂O+4H₂which produces a theoretical 4.0 weight % and a +21 kJ/mol-H₂.

Alternate preferred embodiments of the present invention include varyingthe stoichiometry of the starting material reactant hydride andhydroxide to produce higher-order complex oxide products. Thus, forexample, a complex hydride, such as for example, lithium borohydride(LiBH₄) reacts with a hydroxide, for example boron hydroxide B(OH)₃(i.e., boric acid H₃BO₃) to form a higher-order complex oxide compoundaccording to the following reaction mechanism:3LiBH₄+4H₃BO₃→Li₃B₇O₁₂+12H₂which produces the complex higher-order oxide compound Li₃B₇O₁₂ and atheoretical 7.6 wt. % of hydrogen.

Yet another preferred embodiment comprises a hydroxide where MII is arelatively low molecular weight organic group, such as, methyl, ethyl,and propyl groups. One example of such a hydrogen production reaction,where the hydride composition is selected to be lithium hydride (LiH)and the hydroxide composition is selected to be methanol (CH₃OH) thereaction proceeds according to the following alcoholysis mechanism:LiH+CH₃OH→LiOCH₃+H₂.

As appreciated by one of skill in the art, any number of variations ofhydride and hydroxide combinations are contemplated by the presentinvention, and may include any number of combinations of MI and MIIselections. Further, the hydroxide compositions or the hydridecompositions may comprise mixtures of hydroxide or hydride compounds.For example, the hydroxide compositions may comprise a plurality ofdistinct hydroxide compounds (e.g. LiOH, NaOH) mixed with one anotherfor reacting with a hydride composition. Thus, the embodiments disclosedabove are merely exemplary of a wide range of species which are usefulith the hydrogen storage material composition of the overall presentinvention.

Another preferred embodiment of the present invention provides ahydroxide composition which comprises a hydrated hydroxide which reactswith a hydride. Many hydroxide compounds readily form hydratedcompounds, due to their hydroscopic nature. It is preferred that thehydrated hydroxide compound comprises at least a portion of thehydroxide compound (i.e., that the starting material hydroxide is amixture of non-hydrated hydroxide and hydrated hydroxide), or in analternate embodiment that hydrated hydroxide comprises all of thehydroxide composition starting material. A hydrated hydroxide increasesthe density of hydrogen stored within the hydrogen storage materialincreases hydrogen content, but likewise increases the weight of thematerial and potentially increases the heat evolved. The heat evolvedfrom the hydrated hydroxide compounds may be beneficial to offsetcertain endothermic reaction systems, thereby reducing the overallenthalpy and heat of reaction.

Although not wishing to be bound by any particular theory, it istheorized that the water of hydration attached to the hydroxide reactswith a portion of the hydride in a first exothermic initiation reaction,which produces heat and hydroxide. The remaining portion of hydride (nowdehydrated) is available to react in a hydrogen production reaction withthe hydroxide. Thus, the starting material compositions comprise ahydride MI^(x)H^(x)and a hydrated hydroxide MII^(y)(OH)_(y).wH₂O, wherey represents the average valence state of MII to maintain chargeneutrality of the hydroxide compound and w represents a stoichiometricamount of water. A first portion of the hydride reacts with thehydration water to provide heat to the surrounding starting material andto form a hydroxide product. The remaining portion of the hydride reactswith the hydroxide which comprises the newly formed product from theinitiation reaction, as well as the initial hydroxide provided in thestarting material. Thus, the heat of reaction is more exothermic in theembodiment where the hydroxide is hydrated, versus the embodiment wherethe hydroxide is dehydrated.

The reaction proceeds according to the following:${{\left( {y + {2w}} \right){MI}^{x}H_{x}} + {{{{xMII}^{y}({OH})}_{y} \cdot {wH}_{2}}O}}->{{\frac{x\left( {y + {2w}} \right)}{2}M_{\frac{2}{x}}O} + {\frac{xy}{2}{MII}_{\frac{2}{y}}O} + {\frac{x\left( {y + {2w}} \right)}{2}H_{2}}}$where as previously discussed, x is the average valence state of MI andy is the average valence state of MII, where the average valence statemaintains the charge neutrality of the compound, and where w is astoichiometric amount of water present in the hydrated hydroxidecompound.

Preferred hydride compositions for the present embodiment are the sameas those described above in previous embodiments. Particularly preferredhydride compounds comprise LiH, LiBH₄, NaBH₄, MgH₂, NaH, and mixturesthereof. Preferred hydrated hydroxide compounds comprise primarily thesame cationic species as those discussed in the non-hydrated hydroxideembodiments above, including aluminum (Al), arsenic (As), boron (B),barium (Ba), beryllium (Be), calcium (Ca), cadmium (Cd), cerium (Ce),cesium (Cs), copper (Cu), europium (Eu), iron (Fe), gallium (Ga),gadolinium (Gd), germanium (Ge), hafnium (Hf), mercury (Hg), indium(In), potassium (K), lanthanum (La), lithium (Li), magnesium (Mg),manganese (Mn), sodium (Na), neodymium (Nd), nickel (Ni), lead (Pb),praseodymium (Pr), rubidium (Rb), antimony (Sb), scandium (Sc), selenium(Se), silicon (Si), samarium (Sm), tin (Sn), strontium (Sr), thorium(Th), titanium (Ti), thallium (TI), tungsten (W), yttrium (Y), ytterbium(Yb), zinc (Zn), zirconium (Zr), and mixtures thereof.

Preferred hydrated hydroxide compounds according to the presentinvention include, by way of example, Ba(OH)₂.3H₂O, Ba(OH)₂.H₂O, KOHH₂O, NaOH H₂O. Particularly preferred hydrated hydroxide compoundscomprise: LiOH.H₂O and NaOH.H₂O. The hydrated hydroxide may also form acomplex cationic hydrated hydroxide compound comprising complex cationicspecies, such that MII comprises two cationic species. Examples of suchcomplex cationic hydrated hydroxide compounds include, LiAl₂(OH)₇.2H₂Oand Mg₆Al₂(OH)₁₈.4H₂O. It should be noted that the quantity of water inthe hydrated compound may comprise more than one molecule of water(i.e., that w, the stoichiometric ratio of water, may vary), dependingon the hydroxide compound and its propensity for hydration. The presentinvention further contemplates mixtures of hydrated hydroxide compounds(as well, as alternate embodiments having mixtures of hydrated andnon-hydrated hydroxide compounds, which were previously describedabove).

Certain preferred reactions according to the present embodiment, includethose where a hydrated hydroxide compound reacts with a hydridecompound. The following non-limiting examples are where the hydridecomposition is MI^(x)H^(x) and the hydrated hydroxide is represented byMII^(y)(OH)_(y).zH₂O, and where MII is selected to be lithium:3LiH+LiOH.H₂O→2Li₂O+3H₂which produces a theoretical 9.0 weight % and a ΔH_(r) of −45.2kJ/mol-H₂. Another reaction according to the present embodiment iswhere:3MgH₂+2LiOH.H₂O→3MgO+Li₂O+6H₂which produces a theoretical 7.4 weight % and a ΔH_(r) of −99 kJ/mol-H₂.Yet another reaction with a hydrated hydroxide is as follows:6NaH+2LiOH.H₂O→3Na₂O+Li₂O+6H₂which produces a theoretical 5.3 weight % and a ΔH_(r) of +11 kJ/mol-H₂.Yet another reaction is:3LiBH₄+4LiOH.H₂O→3LiBO₂+2Li₂O+12H₂which produces a theoretical 10.2 weight % and an exothermic ΔH_(r) of−43.5 kJ/mol-H₂.

Similar examples of reactions where the hydrated hydroxide comprises MIIselected to be sodium proceed as follows:6LiH+2NaOH.H₂O→3Li₂O+Na₂O+6H₂which produces a theoretical 7.3 weight % and an exothermic ΔH_(r) of−34.2 kJ/mol-H₂. A similar reaction which is endothermic is as follows:3NaH+NaOH.H₂O→2Na₂O→3H₂which produces a theoretical 4.6 weight % and a ΔH_(r) of +22.0kJ/mol-H₂. Another preferred exothermic reaction is as follows:3NaBH₄+4NaOH.H₂O→3NaBO₂+2Na₂O+12H₂which produces a theoretical 6.9 weight % and an exothermic ΔH_(r) of−21.4 kJ/mol-H₂.

Alternate preferred embodiments of the present invention contemplate amixture of starting material hydroxide comprising hydrated hydroxide andnon-hydrated hydroxide starting materials which react with hydrides toproduce hydrogen and a “complex oxide”, meaning the oxide has higherorder atomic ratio of oxygen to cationic species as compared to thesimple oxides of the previous embodiments, as recognized by one of skillin the art. Such a reaction system includes both the general reaction ofthe hydride plus hydroxide (a first hydrogen generation reaction)${{{yMI}^{X}H_{x}} + {{xMII}^{y}({OH})}_{y}}->{{{xy}H}_{2} + {\left( \frac{xy}{2} \right){MI}_{(\frac{2}{x})}O} + {\left( \frac{xy}{2} \right){MII}_{(\frac{2}{y})}O}}$and the hydride plus hydrated hydroxide (a second hydrogen generationreaction)${{\left( {y + {2w}} \right){MI}^{x}H_{x}} + {{{{xMII}^{y}({OH})}_{y} \cdot {wH}_{2}}O}}->{{\frac{x\left( {y + {2w}} \right)}{2}M_{\frac{2}{x}}O} + {\frac{xy}{2}{MII}_{\frac{2}{y}}O} + {\frac{x\left( {y + {2w}} \right)}{2}H_{2}}}$where the starting reactant material compositions, comprising hydrides,hydroxides, and hydrated hydroxides, can be combined in any number ofproportions to conduct both the first and second hydrogen generationsconcurrently. With such a combination of reactions, the amount of heatrelease can be designed by accounting for the quantities of reactantsadded and the corresponding heat of reaction for both the first andsecond hydrogen production reactions. Generally, the second hydrogengeneration reaction where hydrated hydroxide reacts with a hydride isgenerally more exothermic than the first hydrogen generation reactionwhere a non-hydrated hydroxide reaction with a hydride.

Thus, reaction systems, such as those described above, comprise acombination of reactions for both hydrated hydroxide and non-hydratedhydroxides that are useful in designing a reaction to have a targetedoverall heat of reaction. As previously discussed, one aspect of thepresent invention is the minimization of the overall enthalpy of thereaction system, which can be further controlled by adding a selectedmass of hydrated hydroxide to the starting material mixture. Further,the hydrated hydroxides contain a greater amount of hydrogen per formulaunit, and mixtures of hydrated hydroxides with non-hydrated hydroxidescan be designed for larger hydrogen production due to a larger quantityof hydrogen present in the starting materials.

Examples of such combined reaction systems, where both the hydrides ofthe first and second hydrogen production reactions are selected to bethe same, and a hydroxide composition comprises both hydrated andnon-hydrated hydroxides both having the same cationic species such aswhere the cationic species of the hydride is lithium (LiH) and thehydroxides also have lithium (LiOH) according to the present invention,can be expressed in the simplified reaction mechanism:LiBH₄+LiOH+LiOH.H₂O→Li₃BO₃+2Li₂O+4H₂which generates an oxide (Li₂O) and a complex oxide (Li₃BO₃) and atheoretical 9.0% by weight of hydrogen. Yet another example, where thereactants are the same, but provided at a different stoichiometry,produces different products in the following reaction:2LiBH₄+LiOH+2 LiOH.H₂O→Li₄B₂O₅+LiH+7H₂which generates a complex oxide (Li₄B₂O₅), a simple hydride (LiH) and atheoretical 9.2% by weight hydrogen.

The present invention provides a mixture of a hydride and a hydroxidehaving cationic species other than hydrogen, each one characterized bypromoting the release of hydrogen from the other one, in the presenceof: a catalyst, elevated temperature, or both.

The present invention also provides a method of producing a source ofhydrogen gas comprising liberating hydrogen from a hydrogenated startingmaterial comprising a hydride and a hydroxide, where the hydroxide hasone or more cationic species other than hydrogen and by reacting thehydride with the hydroxide to produce a dehydrogenated product andhydrogen gas. In certain preferred embodiments, the hydrogenatedstarting material composition can be regenerated by exposing thedehydrogenated product (which preferably comprises an oxide composition)to hydrogen gas. As the liberating proceeds, it is preferred that thehydrogen gas is removed, both to collect the hydrogen gas as fuel forthe fuel cell, and in some reaction systems to drive the reactionforward. The liberation of hydrogen gas can be conducted in the presenceof an appropriate catalyst contacting the starting material compositionto facilitate hydrogen release.

In preferred embodiments of the present invention, a hydrogen productionreaction is conducted by a solid-state reaction, where the startingmaterials are in particulate form. The desirable particle size of thestarting materials is related to its hydrogen release performance.Particles which are too coarse extend the time for the hydrogen releasereaction at a given temperature. As will be discussed in more detailbelow, a smaller particle size may contribute to overcoming activationenergy barriers by increasing the surface area interface between thehydrogenated starting material reactants. Further, it is preferred thatthe starting material reactants are essentially homogeneously mixedtogether, to enhance the reactivity of the mixture of hydrogenatedstarting material reactants. By “essentially homogeneously mixed” it ismeant that the different starting material reactants are distributedwith one another sufficiently that the reaction rate is notsignificantly inhibited by isolation of reactant particles from oneanother. It is preferred that starting material particles have a size onthe order of 100 micrometers (μm), which can be achieved by ball millingfor 1 to 10 hours, for example, to form a suitable starting material.Preferably the particle size of the reactants is on the order of lessthan about 10 micrometers, and most preferably less than 1 micrometer.

EXAMPLE 1

This example demonstrates the hydrogen storage material system where MIand MII are selected to be lithium in the hydrogen storage materialsystem. An equal molar ratio of lithium hydride (LiH) and lithiumhydroxide (LiOH) were weighed at 0.248 g of LiH and 0.756 g of LiOH andwere mixed to form the hydrogenated mixture the hydrogen storage mediasystem, that releases hydrogen according to the following reaction toproduce hydrogen:LiH+LiOH→Li₂O+H₂.The mixing was accomplished using standard ball milling techniques atroom temperature under ambient conditions for 60 minutes. Some hydrogengeneration was noted during the milling process. The mixture was thenheated at a rate of 2° C. per minute up to a maximum temperature of 300°C. while under ambient conditions and analyzed by a modified Sievert'sapparatus, where the volumetric gas absorption is measured and convertedto a weight percentage.

This analysis is shown in FIG. 1, where a total of 5.3 weight % wasgenerated (with the difference between the theoretical 6.25 weight %being attributed to the hydrogen generated and either lost during themilling process or due to impurities in the starting materials). Fromthe graph, it is apparent that hydrogen generation begins at about 80°C. and accelerates at approximately 170° C.

EXAMPLE 2

The hydrogen storage material system is the same as that in Example 1.Equal molar ratios of lithium hydroxide (LiOH) and lithium hydride (LiH)with measured amounts of 0.249 g LiH and 0.749 g of LiOH were mixedtogether and mechanically milled using the same ball milling techniquesas described in Example 1, except that the mixture was milled for ashorter duration of 12 minutes.

EXAMPLE 3

A hydrogen storage material system where the hydride is lithium hydride(LiH) and the hydroxide is lithium hydroxide (LiOH), similar to Example2 above, is reacted in the presence of a catalyst, titanium chloride,TiCl₃. A mixture of an equal molar ratio of lithium hydride (LiH) andlithium hydroxide (LiOH) weighed as 0.201 g LiH and 0.611 g of LiOH weremixed with one another. The catalyst was further added during milling at10 mol % weighed at 0.385 TiCl₃, and the entire mixture was then milledfor 12 minutes.

The resulting samples from Examples 2 and 3 were subjected to a modifiedSievert's analysis, where heat was applied in increasing steps. Thefirst heating step reached a temperature of 100° C. (point A), thesecond step ramps up to 200° C. (point B) and then the final stepreached 250° C. (point C). As can be observed from the data, thehydrogen generation began at approximately 80° C. for the Sample fromExample 2 without a catalyst. As the temperature was held constantthrough the first step at 100° C., the rate of hydrogen generation inthe Example 2 Sample slowed reaching only approximately 0.7 weightpercent. Increasing the temperature to the next step of 200° C.increased the amount of hydrogen generated, but as the sample remainedat 200° C. the rate of hydrogen generation slowed. As the sampletemperature was again elevated, to the 250° C. interval, a similarbehavior was observed, where hydrogen production slowed at constanttemperature. After increasing to 250° C., 5.7 wt. % of hydrogen wasgenerated. This amount is closer to the theoretical hydrogen amount of6.25 wt. % and the amount in Example 1, and is attributed to lesshydrogen generated or lost during the milling process.

The data shown in FIG. 2 suggests that there is an activation energybarrier for this exothermic reaction that occurs at about 80° C., wherethe hydrogen release initiates. As can be observed from the data, thepresence of a catalyst during the hydrogen generation reactionsignificantly accelerates hydrogen evolution. For example, at 100° C.,only approximately 0.7 wt. % hydrogen was produced for the mixture madein Example 2 without a catalyst, as where approximately 2.7 wt. %hydrogen was generated at 100° C. for the mixture of Example 3 with 10mol. % catalyst. The overall lower quantity of hydrogen produced in theExample 3 sample is likely attributed to premature production ofhydrogen during the milling process.

The behavior of the hydrogen storage material system in both FIGS. 1 and2 shows that the hydrogen production reaction is kinetically limited.The sample from Example 3 where the catalyst was added demonstrates thatthe catalyst facilitates greater hydrogen release at relatively lowtemperatures. Due to the fact that the hydrogen production reaction inthe lithium hydride and lithium hydroxide system is exothermic, thethermodynamic equilibrium state corresponds to a nearly completereaction at room temperature. It is also possible that product (such as,solid phase byproduct oxide composition or hydrogen gas) accumulatingwhere the reaction is occurring in the hydrogen storage material mixturemay inhibit full release of hydrogen from the storage material. Thereaction can be driven towards complete release of hydrogen byaddressing both the activation energy barrier and the inhibition byproduct build-up through various means recognized by one of skill in theart.

For example, as previously discussed, mixing the solid reactantparticles in an essentially homogenous mixture on a fine scalefacilitates greater hydrogen release from the hydrogen storagecompositions. Also, suitable catalysts (such as the TiCl₃ in Example 3)may be selected to facilitate the reaction and drive it to completion byovercoming any initiation/activation energy barriers. Exemplarycatalysts suitable for use with the present invention include forexample, compounds comprising elements selected from the groupconsisting of Ti, V, Cr, C, Fe, Mn, Ni, Si, Al, Nb, Pd, and mixturesthereof. Such catalyst compounds may be selected in elemental form, ormay comprise hydride, halide, oxide, or nitride compounds, for example.A non-limiting list of such catalyst compounds includes: TiCl₃, TiO₂,TiN, V₂O₅, SiO₂, Nb₂O₅, and Al₂O₃, for example.

Further, products may be removed as the reaction proceeds. For example,hydrogen gas will easily be removed, and methods of solid-solidseparation recognized by one of skill in the art may be employed toaddress the accumulation of solid phase oxide compositions in thehydrogen storage materials. Additionally, as will be discussed ingreater detail below, one preferred embodiment of the present inventioninitiates the hydrogen production reaction by providing heat via asecond exothermic reaction to overcome the activation energy barrier ofthe hydrogen production reaction. This exothermic initiation reactiontransfers heat to the solid-state reactants in an amount sufficient toinitiate the subsequent hydrogen generation reaction with one another.

EXAMPLE 4

In Example 4, a mixed cation hydrogen storage material system isprovided where MI is selected to be sodium and MII is selected to thelithium. An equal molar ratio of sodium hydride (NaH) and lithiumhydroxide (LiOH) weighed as 0.655 g NaH and 0.652 g of LiOH, was mixedand ground by conventional ball milling techniques. A considerableamount of hydrogen generation was noted during the milling process (byan audible gas release when opening the milling vessel). The milledmixture was then analyzed by a modified Sievert's apparatus as shown inFIG. 3. As can be observed from the data, hydrogen generation begins atapproximately 40° C. (point A) and is complete at approximately 100° C.(point B). Approximately 0.8 wt. % of hydrogen was generated, which isless than the theoretical yield of 4.1 weight percent, however as notedabove, a large unquantified amount of hydrogen was produced duringmilling, which would likely approach the theoretical yield whenaccounted for.

EXAMPLE 5

A mixed cation hydrogen storage material system where the hydride is acomplex hydride (i.e., lithium borohydride where MI is selected to belithium) and a hydroxide where MII is selected to the lithium forminglithium hydroxide. An equal molar ratio of lithium borohydride (LiBH₄)and lithium hydroxide (LiOH) weighed as 0.224 g LiBH₄ and 0.981 g ofLiOH, was mixed and then milled for 1 hour. The sample of Example 5 wasanalyzed by a modified Sievert's analysis as the results shown in FIG.4. Hydrogen generation appears to commence at approximately 250° C.,however, with addition of a catalyst (such as in Example 3), thereaction kinetics should be modified to produce hydrogen at lowertemperatures. A maximum of 6.6 wt. % hydrogen was produced, which isclose to the theoretical yield of 6.8 wt. %.

In accordance with the behavior observed during the Sievert's testing ofthe hydrogen storage material systems, it is preferred that the hydrogenproduction reaction between the hydroxide compositions and hydridecompositions is conducted at an elevated temperature above ambientconditions, primarily to increase the rate of reaction, as well asovercoming any initiation activation barriers. Although this specifictemperature varies for the thermodynamics of the particular reaction,which is dependent upon the cationic species selected, certain preferredembodiments of the present invention conduct a reaction at a temperatureof above about 40° C. Other preferred embodiments of the presentinvention preferably are conducted at a temperature of about 80° C. orhigher.

Additionally, a compressive force may be applied on the solid startingmaterials while conducting the hydrogen production reaction of thepresent invention to increase physical contact between the particles andto enhance the reaction. However, in such an embodiment wherecompressive force is applied to the starting materials, it is preferredthat the compressive force is applied in such a manner so as not toprevent hydrogen gas formation or release. For example, the compressiveforce may be applied with platens formed of porous material, whichpermits gas to travel therethrough, as it is generated within thestarting materials.

The present invention further provides a method of producing hydrogenwhich comprises reacting a first portion of a starting materialcomprising a hydride with water. This first initiation reaction betweenthe first portion of the hydride and water is spontaneous andexothermic, generating approximately 165 kJ/mol-H₂ in the heat ofreaction, which provides heat to the surrounding starting materials.This generated heat provides the necessary enthalpy to overcome theenergy activation barrier of the hydrogen production reaction between aremaining second portion of hydride and a hydroxide. The hydrogenproduction reaction may be exothermic or endothermic. The first reactioncommences the second reaction, and in certain preferred embodiments, thefirst reaction proceeds essentially simultaneously or concurrently withthe second reaction.

The total amount of hydride present in the starting material comprisesthe first and second portions. In preferred embodiments of the presentinvention, the total amount of hydride present in the starting material,includes the first portion which reacts with water in a molar amountdesignated “n”, so that in the example where MI and MII are the samecationic species, M, having an average valence state of “w” theinitiation reaction would proceed by the following mechanism:nM^(z)H_(z) +nH₂O'nM^(z)(OH)_(z)+2nH₂.For example, where the cationic species MI and MII are selected to belithium (Li) for both the hydride and hydroxide, and n=0.5, the reactioncan be expressed as0.5 LiH+0.5H₂O→0.5 LiOH+0.5H₂.The molar amount of hydride added is preferably correlated to how muchheat is needed to initiate the second hydrogen production reaction, anddepends upon the overall mass of reactants present in the startingmaterial for the second hydrogen production reaction. The value of “n”can be adjusted to heat the starting material mixture to the desiredreaction initiation temperature.

The first initiation reaction generates “n” moles of hydroxide, producedby a reaction between “n” moles of water and “n” moles of hydride. Toaccount for the hydride consumed in the first reaction with water, aswell as the hydroxide produced by the first reaction, the startinghydrogen storage materials in the hydrogen production reaction can beadjusted by the following molar proportions:(1+n)M_(z)H_(z)+(1−n)M^(z)(OH)_(z) →zM₂O+zH₂,where n moles of hydride is consumed in the heat generation reaction,while reacting with n moles of water to generate and n moles ofhydroxide, where z moles of oxide and hydrogen are each produced, suchthat the molar amount of hydride consumed in the initiation reaction(and corresponding to a sufficient enthalpy to initiate the secondreaction) or the hydroxide formed in the heat generation reaction iscompensated for in the second reaction. Thus, in the heat generationreaction, where n=0.5, the reaction proceeds as0.5LiH+0.5H₂O→0.5 LiOH+0.5H₂,where 0.5 LiH was consumed as a first portion of the hydride startingmaterial and 0.5 LiOH was generated for use in the hydrogen productionreaction. Thus, the hydrogen production reaction proceeds according to:LiH+LiOH→Li₂O+H₂.

It is preferred that the hydrogen production reaction proceeds tosubstantial completion and that the hydride (and likewise the hydroxide)reactant is substantially consumed. By “substantial” and“substantially”, it is meant that the reaction proceeds and reactant areconsumed in the reaction to an industrially practical level, expected byone of skill in the art. Thus, the resulting mixture has the exactstoichiometry needed for the hydrogen production reaction to proceedessentially to completion by essentially all of the reactants formingproducts. Further, the molar amount of hydroxide generated in the firstinitiation reaction is likewise accounted for in the second hydrogenproduction reaction. It should be noted that the present invention isequally applicable to situations where MI and MII are selected to bedifferent cationic species from one another, and as one of skill in theart would appreciate, the hydroxide generated may form a mixture ofhydroxide reactants (e.g., nMI^(x)(OH)_(x) and MII^(y)(OH)_(y) whichcombined together, respectively react with the hydride MI^(x)H^(x)),which likewise generate a byproduct compound in the second hydrogengeneration reaction that comprises mixtures of oxide compositions(having mixed cationic species, or mixtures of distinct oxidecompositions with different cationic species). Such alternate preferredembodiments where MI and MII are different from one another, may resultin a modification to the thermodynamics of the hydrogen productionreaction, by introducing another reactant into the reaction, asappreciated by one of skill in the art. Thus, in the present embodimentof the present invention, a total amount of hydride in the startingmaterial composition comprises the first and second portions of thehydride, where the first portion reacting with water is preferablydictated by the amount of thermal energy necessary to initiate and causethe hydrogen production reaction, and the second portion of hydride isan amount sufficient to react with both the hydroxide generated in theinitiation reaction and the amount provided for the hydrogen productionreaction.

Alternate preferred embodiments may include additional amounts of aparticular reactant, not in accordance with the molar stoichiometrydiscussed in the embodiment above, such as for example, providing excesshydride for ensuring the reaction proceeds to completion. Otherconsiderations may include providing more reactant in reactions wherethe presence of the reactant impact the reaction rate, or the reactantmay have physical limitations, such as a larger particle size ordifficulty in homogeneously mixing.

Preferred embodiments of the present invention thus provide a method ofproducing hydrogen by generating heat in a first reaction by reactingwater with a portion of a hydride present in a first materialcomposition, wherein the heat is used in a second hydrogen productionreaction. A remaining portion of the hydride present in the firstmaterial composition is reacted with a hydroxide having one or morecations other than hydrogen present in a second material composition bya hydrogen production reaction, which forms a hydrogen product and abyproduct composition comprising an oxide. One preferred aspect of thepresent invention is that the combined hydrogen storage system,including a water initiation reaction, is hydrogen rich. The waterreacting with hydride also produces hydrogen, which increases the totalamount of hydrogen produced by the hydrogen storage material system.

The water for the first exothermic initiation reaction may be added tothe solid phase starting material mixture, as a liquid reactant. It ispreferred that the water is generally evenly distributed throughout thestarting material mixture to provide even heat to the surroundingparticles. However, in alternate embodiments where the hydrogenproduction reaction is exothermic, it is possible that only a relativelysmall portion of the starting material hydride is heated to above thereaction initiation temperature. As the initiation temperature causesthe hydrogen production reaction in nearby reactant particles, heat willbe generated by the hydrogen production reaction, and further betransferred to the surrounding starting material, thus providing thenecessary activation energy to start the hydrogen production reaction inthe surrounding material.

In alternate preferred embodiments of the present invention, the watermay be provided as water of hydration in one of the starting materials.The water of hydration then reacts with the hydride material. It ispreferred that the hydrated compound is the hydroxide compound, many ofwhich are hydroscopic and readily form hydrated compounds. Although notwishing to be limited by any particular theory, it appears that thewater of hydration attached to the hydroxide reacts with a portion ofthe hydride in a first exothermic initiation reaction, which producesheat and hydroxide. The remaining portion of hydride (now dehydrated) isavailable to react in a hydrogen production reaction with the hydroxide.The water of hydration attached to the hydroxide reacts with a portionof the hydride in a first exothermic initiation reaction, which producesheat and hydroxide.

Thus, the starting material mixture has a hydrated hydroxide and ahydride mixed together with one another. The starting materialcompositions comprise a hydride MI^(x)H^(x) and a hydrated hydroxideMII^(y)(OH)_(y)-wH₂O, where y represents the average valence state ofMII to maintain charge neutrality of the hydroxide compound and wrepresents a stoichiometric amount of water. A first portion of thehydride reacts with the hydration water to provide heat to thesurrounding starting material and to form a hydroxide product. Theremaining portion of the hydride reacts with the hydroxide whichcomprises the newly formed product from the initiation reaction, as wellas the initial hydroxide provided in the starting material. In thepresent embodiment, it is contemplated that the heat generation reactionand the hydrogen production reaction behave as one reaction, rather thantwo distinct reactions.

The reaction proceeds according to the following:${{\left( {y + {2w}} \right){MI}^{x}H_{x}} + {{{{xMII}^{y}({OH})}_{y} \cdot {wH}_{2}}O}}->{{\frac{x\left( {y + {2w}} \right)}{2}M_{\frac{2}{x}}O} + {\frac{xy}{2}{MII}_{\frac{2}{y}}O} + {\frac{x\left( {y + {2w}} \right)}{2}H_{2}}}$where as previously discussed, x is the average valence state of MI andy is the average valence state of MII, where the average valence statemaintains the charge neutrality of the compound, and where w is astoichiometric amount of water present in the hydrated hydroxidecompound.

Preferred hydride compositions for the present embodiment are the sameas those described above in previous embodiments. Particularly preferredhydride compounds comprise LiH, LiBH₄, NaBH₄, MgH₂, NaH, and mixturesthereof. Preferred hydrated hydroxide compounds comprise primarily thesame cationic species as those discussed in the non-hydrated hydroxideembodiments above, including aluminum (Al), arsenic (As), boron (B),barium (Ba), beryllium (Be), calcium (Ca), cadmium (Cd), cerium (Ce),cesium (Cs), copper (Cu), europium (Eu), iron (Fe), gallium (Ga),gadolinium (Gd), germanium (Ge), hafnium (Hf), mercury (Hg), indium(In), potassium (K), lanthanum (La), lithium (Li), magnesium (Mg),manganese (Mn), sodium (Na), neodymium (Nd), nickel (Ni), lead (Pb),praseodymium (Pr), rubidium (Rb), antimony (Sb), scandium (Sc), selenium(Se), silicon (Si), samarium (Sm), tin (Sn), strontium (Sr), thorium(Th), titanium (Ti), thallium (TI), tungsten (W), yttrium (Y), ytterbium(Yb), zinc (Zn), zirconium (Zr), and mixtures thereof.

Preferred hydrated hydroxide compounds according to the presentinvention include, by way of example, Ba(OH)₂.3H₂O, Ba(OH)₂.H₂O,KOH.H₂O, NaOH.H₂O. Particularly preferred hydrated hydroxide compoundscomprise: LiOH.H₂O and NaOH.H₂O. The hydrated hydroxide may also form acomplex cationic hydrated hydroxide compound comprising complex cationicspecies, such that MII comprises two cationic species. Examples of suchcomplex cationic hydrated hydroxide compounds include, LiAl₂(OH)₇.2H₂Oand Mg₆Al₂(OH)₁₈.4H₂O. It should be noted that the quantity of water inthe hydrated compound may comprise more than one molecule of water(i.e., that z, the stoichiometric ratio of water, may vary), dependingon the hydroxide compound and its propensity for hydration. The presentinvention further contemplates mixtures of hydrated hydroxide compounds(as well, as alternate embodiments having mixtures of hydrated andnon-hydrated hydroxide compounds, which were previously describedabove).

Further, for many hydride and hydrated hydroxide species there is agreater energy activation barrier than for the independent reactantwater to the heat generation reaction, which requires additional heat orother means to overcome the initiation barrier to commence the heatgeneration reaction. This additional energy may include the energyrequired to disassociate the hydrated water molecules from the hydroxidemolecules. Such initiation energy may be provided by any known means, aspreviously discussed (e.g., heat, reduced particle size, catalysts, andthe like) or by adding some liquid water to generate heat to start thereactions between the hydrated hydroxide and the hydride. Thus, a firstportion of water may be in the form of a hydrated hydroxide and a secondportion of water may be provided as a liquid reactant added to thehydrated hydroxide and hydride materials.

In preferred embodiments of the present invention, It is preferred thatthe hydrated hydroxide compound comprises at least a portion of thehydroxide compound (i.e., that the starting material hydroxide is amixture of non-hydrated hydroxide and hydrated hydroxide), or in analternate embodiment that hydrated hydroxide comprises all of thehydroxide composition starting material. A hydrated hydroxide increasesthe density of hydrogen stored within the hydrogen storage materialincreases hydrogen content, but likewise increases the weight of thematerial and potentially increases the heat evolved. Generally, the heatof reaction is more exothermic in the embodiment where the hydroxide ishydrated, versus the embodiment where the hydroxide is dehydrated. Theheat evolved from the hydrated hydroxide compounds may be beneficial tooffset certain endothermic reaction systems, thereby reducing theoverall enthalpy and heat of reaction.

Certain preferred reactions according to the present embodiment, includethose where a hydrated hydroxide compound reacts with a hydridecompound. The following non-limiting examples are where the hydridecomposition is MI^(x)H^(x) and the hydrated hydroxide is represented byMII^(y)(OH)_(y).wH₂O, and where MII is selected to be lithium:3LiH+LiOH.H₂O.2Li₂O→3H₂which produces a theoretical 9.0 weight % and a ΔH_(r) of −45.2kJ/mol-H₂. Another reaction according to the present embodiment iswhere:3MgH₂+2LiOH.H₂O→3MgO+Li₂O+6H₂which produces a theoretical 7.4 weight % and a ΔH_(r) of −99 kJ/mol-H₂.Yet another reaction with a hydrated hydroxide is as follows:6NaH+2LiOH.H₂O→3Na₂O+Li₂O+6H₂which produces a theoretical 5.3 weight % and a ΔH_(r) of +11 kJ/mol-H₂.Yet another reaction is:3LiBH₄+4LiOH.H₂O→3LiBO₂+2Li₂O+12H₂which produces a theoretical 10.2 weight % and an exothermic ΔH_(r) of−43.5 kJ/mol-H₂.

Similar examples of reactions where the hydrated hydroxide comprises MIIselected to be sodium proceed as follows:6LiH+2NaOH.H₂O→3Li₂O+Na₂O+6H₂which produces a theoretical 7.3 weight % and an exothermic ΔH_(r) of−34.2 kJ/mol-H₂. A similar reaction which is endothermic is as follows:3NaH+NaOH.H₂O→2Na₂O+3H₂which produces a theoretical 4.6 weight % and a ΔH_(r) of +22.0kJ/mol-H₂. Another preferred exothermic reaction is as follows:3NaBH₄+4NaOH.H₂O→3NaBO₂+2Na₂O+12H₂which produces a theoretical 6.9 weight % and an exothermic ΔH_(r) of−21.4 kJ/mol-H₂.

Alternate preferred embodiments of the present invention contemplate amixture of starting material hydroxide comprising hydrated hydroxide andnon-hydrated hydroxide starting materials which react with hydrides toproduce hydrogen and a “complex oxide”, meaning the oxide has higherorder atomic ratio of oxygen to cationic species as compared to thesimple oxides of the previous embodiments, as recognized by one of skillin the art. Such a reaction system includes both the general reaction ofthe hydride plus hydroxide (a first hydrogen generation reaction)${{{yMI}^{X}H_{x}} + {{xMII}^{y}({OH})}_{y}}->{{{xy}H}_{2} + {\left( \frac{xy}{2} \right){MI}_{(\frac{2}{x})}O} + {\left( \frac{xy}{2} \right){MII}_{(\frac{2}{y})}O}}$and the hydride plus hydrated hydroxide (a second hydrogen generationreaction)${{\left( {y + {2w}} \right){MI}^{x}H_{x}} + {{{{xMII}^{y}({OH})}_{y} \cdot {wH}_{2}}O}}->{{\frac{x\left( {y + {2w}} \right)}{2}M_{\frac{2}{x}}O} + {\frac{xy}{2}{MII}_{\frac{2}{y}}O} + {\frac{x\left( {y + {2w}} \right)}{2}H_{2}}}$where the starting reactant material compositions, comprising hydrides,hydroxides, and hydrated hydroxides, can be combined in any number ofproportions to conduct both the first and second hydrogen generationsconcurrently. With such a combination of reactions, the amount of heatrelease can be designed by accounting for the quantities of reactantsadded and the corresponding heat of reaction for both the first andsecond hydrogen production reactions. Generally, the second hydrogengeneration reaction where hydrated hydroxide reacts with a hydride isgenerally more exothermic than the first hydrogen generation reactionwhere a non-hydrated hydroxide reaction with a hydride.

Thus, reaction systems, such as those described above, comprise acombination of reactions for both hydrated hydroxide and non-hydratedhydroxides that are useful in designing a reaction to have a targetedoverall heat of reaction. As previously discussed, one aspect of thepresent invention is the minimization of the overall enthalpy of thereaction system, which can be further controlled by adding a selectedmass of hydrated hydroxide to the starting material mixture. Further,the hydrated hydroxides contain a greater amount of hydrogen per formulaunit, and mixtures of hydrated hydroxides with non-hydrated hydroxidescan be designed for larger hydrogen production due to a larger quantityof hydrogen present in the starting materials.

Examples of such combined reaction systems, where both the hydrides ofthe first and second hydrogen production reactions are selected to bethe same, and a hydroxide composition comprises both hydrated andnon-hydrated hydroxides both having the same cationic species such aswhere the cationic species of the hydride is lithium (LiH) and thehydroxides also have lithium (LiOH) according to the present invention,can be expressed in the simplified reaction mechanism:LiBH₄+LiOH+LiOH.H₂O→Li₃BO₃+2Li₂O+4H₂which generates an oxide (Li₂O) and a complex oxide (Li₃BO₃) and atheoretical 9.0% by weight of hydrogen. Yet another example, where thereactants are the same, but provided at a different stoichiometry,produces different products in the following reaction:2LiBH₄+LiOH+2LiOH.H₂O→Li₄B₂O₅+LiH+7H₂

-   -   which generates a complex oxide (Li₄B₂O₅), a simple hydride        (LiH) and a theoretical 9.2% by weight hydrogen.

Thus, the hydrogen storage materials according to the present inventionprovide solid phase hydrogen storage, which is especially advantageousin fuel cell applications, particularly in mobile fuel-cellapplications. Such hydrogen storage material compositions are generallywidely available, and of relatively low molecular weight, whichfacilitates improving the efficiency of the fuel-cell unit.Additionally, the system of hydrogen production reactions available fromthe variants of the present invention have relatively low total enthalpychanges, which reduces the need for extensive control and coolingsystems, as well as eliminating parasitic energy demands from thefuel-cell system. Further, the release of hydrogen from the hydrogenstorage material systems is readily facilitated by an exothermicinitiation reaction with a commonly available hydrogen containingreactant (i.e., water).

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A method of producing hydrogen comprising: reacting a first portionof a hydride with water to produce heat in a first reaction and reactinga second portion of said hydride and a hydroxide in a second reaction,by transferring said heat thereto.
 2. The method according to claim 1wherein said second reaction produces hydrogen.
 3. The method accordingto claim 1 wherein said first reaction produces at least a portion ofsaid hydroxide.
 4. The method according to claim 1 wherein said secondreaction commences while said first reaction is occurring.
 5. The methodaccording to claim 1 wherein said second reaction is exothermic.
 6. Themethod according to claim 1 wherein said second reaction producinghydrogen is endothermic.
 7. The method according to claim 1 wherein saidwater is added to said hydride.
 8. The method according to claim 7wherein said amount of heat generated is greater than or equal to anactivation energy of said second reaction.
 9. The method according toclaim 8 wherein said second reaction proceeds to substantial completionand said second portion of hydride is substantially consumed in saidsecond reaction.
 10. The method according to claim 1 wherein saidhydride is represented by the formula: MI^(x)H^(x), where MI representsone or more cationic species other than hydrogen and x represents anaverage valence state of MI.
 11. The method according to claim 1 whereinsaid hydroxide is represented by the formula: MII^(y)(OH)_(y), where MIIrepresents one or more cationic species other than hydrogen and yrepresents an average valence state of MII.
 12. The method of claim 1wherein said hydride is represented by MI^(x)H^(x) and said hydroxide isrepresented by MII^(y)(OH)_(y), where MI and MII respectively representone or more cationic species other than hydrogen, and x and y representaverage valence states of MI and MII, respectively.
 13. The method ofclaim 1 wherein MI and MII comprise one or more distinct cationicspecies.
 14. The method of claim 1 wherein MI and MII comprise one ormore of the same cationic species.
 15. The method of claim 1 wherein MIor MII is a complex cationic species comprising two distinct cationicspecies.
 16. The method of claim 1 wherein MI is selected from the groupconsisting of CH₃, Al, As, B, Ba, Be, Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga,Gd, Ge, Hf, Hg, In, K, La, Li, Mg, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc,Se, Si, Sm, Sn, Sr, Th, Ti, TI, V, W, Y, Yb, Zn, Zr, and mixturesthereof.
 17. The method of claim 1 wherein MII is selected from thegroup consisting of CH₃, C₂H₅, C₃H₇, Al, As, B, Ba, Be, Ca, Cd, Ce, Cs,Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg, In, K, La, Li, Mg, Mn, Na, Nd, Ni, Pb,Pr, Rb, Sb, Sc, Se, Si, Sm, Sn, Sr, Th, Ti, TI, V, W, Y, Yb, Zn, Zr, andmixtures thereof.
 18. The method of claim 12 wherein MI and MII are eachelements independently selected from the group consisting of Al, B, Be,Ca, K, Li, Mg, Na, Sr, Ti, and mixtures thereof.
 19. The method of claim12 wherein said hydroxide further comprises: MII^(y)(OH)_(y).wH₂O, whereMII represents said one or more cationic species other than hydrogen, yrepresents an average valence state of MII, and w represents astoichiometric amount of hydrated water.
 20. The method according toclaim 1 wherein said hydroxide is represented by the formula:MII^(y)(OH)_(y).wH₂O, where MII represents said one or more cationicspecies other than hydrogen, y represents an average valence state ofMII, and w represents a stoichiometric amount of hydrated water.
 21. Themethod of claim 1 wherein said hydride is represented by MI^(x)H^(x) andsaid hydroxide is represented by MII^(y)(OH)_(y).wH₂O, where MIIrepresents said one or more cationic species other than hydrogen, yrepresents an average valence state of MII, and w represents astoichiometric amount of hydrated water.
 22. The method of claim 21wherein MI is selected from the group consisting of Al, As, B, Ba, Be,Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg, In, K, La, Li, Mg, Mn,Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Si, Sm, Sn, Sr, Th, Ti, TI, V, W, Y,Yb, Zn, Zr, and mixtures thereof.
 23. The method of claim 21 wherein MIIis selected from the group consisting of Al, As, B, Ba, Be, Ca, Cd, Ce,Cs, Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg, In, K, La, Li, Mg, Mn, Na, Nd, Ni,Pb, Pr, Rb, Sb, Sc, Se, Si, Sm, Sn, Sr, Th, Ti, TI, V, W, Y, Yb, Zn, Zr,and mixtures thereof.
 24. The method of claim 21 wherein MI and MII areeach elements independently selected from the group consisting of Al, B,Ba, Be, Ca, Cs, K, Li, Mg, Na, Rb, Si, Sr, Ti, V and mixtures thereof.25. The method of claim 21 wherein MI and MII are each elementsindependently selected from the group consisting of Al, B, Be, Ca, K,Li, Mg, Na, Sr, Ti, and mixtures thereof.
 26. The method according toclaim 1 wherein said hydride is selected from the group consisting of:lithium hydride (LiH), sodium hydride (NaH), potassium hydride (KH),beryllium hydride (BeH₂), magnesium hydride (MgH₂), calcium hydride(CaH₂), strontium hydride (SrH₂), titanium hydride (TiH₂), aluminumhydride (AlH₃), boron hydride (BH₃), lithium borohydride (LiBH₄), sodiumborohydride (NaBH₄), magnesium borohydride (Mg(BH₄)₂), calciumborohydride (Ca(BH₄)₂), lithium alanate (LiAlH₄), sodium alanate(NaAlH₄), magnesium alanate (Mg(AlH₄)₂), calcium alanate (Ca(AlH₄)₂),and mixtures thereof.
 27. The method according to claim 1 wherein saidhydroxide is selected from the group consisting of: composition isselected from the group consisting of: lithium hydroxide (LiOH), sodiumhydroxide (NaOH), potassium hydroxide (KOH), beryllium hydroxide(Be(OH)₂), magnesium hydroxide (Mg(OH)₂), calcium hydroxide (Ca(OH)₂),strontium hydroxide (Sr(OH)₂), titanium hydroxide (Ti(OH)₂), aluminumhydroxide (Al(OH)₃), boron hydroxide (B(OH)₃) and mixtures thereof. 28.The method according to claim 1 wherein said hydride comprises LiH andsaid hydroxide comprises LiOH.
 29. The method according to claim 28wherein said second reaction proceeds according to a reaction mechanismof LiH+LiOH→Li₂O+H₂.
 30. The method according to claim 1 wherein saidhydride comprises NaH and said hydroxide comprises LiOH.
 31. The methodaccording to claim 30 wherein said second reaction proceeds according toa reaction mechanism of NaH+LiOH→½Li₂O+½Na₂O+H₂.
 32. The methodaccording to claim 1 wherein said hydride comprises MgH₂ and saidhydroxide comprises Mg(OH)₂.
 33. The method according to claim 32wherein said second reaction proceeds according to a reaction mechanismof MgH₂+Mg(OH)₂→MgO+2H₂.
 34. The method according to claim 1 whereinsaid hydride comprises AlH₃ and said hydroxide comprises Al(OH)₃. 35.The method according to claim 34 wherein said second reaction proceedsaccording to a reaction mechanism of AlH₃+Al(OH)₃→Al₂O₃+3H₂.
 36. Themethod according to claim 1 wherein said hydride comprises CaH₂ and saidhydroxide comprises Ca(OH)₂.
 37. The method according to claim 36wherein said second reaction proceeds according to a reaction mechanismof CaH₂+Ca(OH)₂→CaO+2H₂.
 38. The method according to claim 1 whereinsaid hydride comprises SrH₂ and said hydroxide comprises Sr(OH)₂. 39.The method according to claim 38 wherein said second reaction proceedsaccording to a reaction mechanism of SrH₂+Sr(OH)₂→SrO+2H₂.
 40. Themethod according to claim 1 wherein said hydride comprises BH₃ and saidhydroxide comprises B(OH)₃.
 41. The method according to claim 40 whereinsaid second reaction proceeds according to a reaction mechanism ofBH₃+B(OH)₃→B₂O₃₊₃H₂.
 42. The method according to claim 1 wherein saidhydride comprises BeH₂ and said hydroxide comprises Be(OH)₂.
 43. Themethod according to claim 42 wherein said second reaction proceedsaccording to a reaction mechanism of BeH₂+Be(OH)₂→BeO+2H₂.
 44. Themethod according to claim 1 where said hydride comprises LiBH₄ and saidhydroxide comprises B(OH)₃.
 45. The method according to claim 44 wheresaid second reaction proceeds according to a reaction mechanism of3LiH+H₃BO₃→LiBO₂+Li₂O+3H₂.
 46. The method according to claim 44 wheresaid second reaction proceeds according to a reaction mechanism of3LiH+H₃BO₃→Li₃BO₃₊₃H₂.
 47. The method according to claim 44 where saidsecond reaction proceeds according to a reaction mechanism of 3LiBH₄₊₄H₃BO₃→Li₃B₇O₁₂+12H₂.
 48. The method according to claim 1 wheresaid hydride comprises LiBH₄ and said hydroxide comprises LiOH.
 49. Themethod according to claim 48 where said second reaction proceedsaccording to a reaction mechanism of LiBH₄₊₄ LiOH→LiBO₂+2Li₂O+4H₂. 50.The method according to claim 1 where said hydride comprises NaBH₄ andsaid hydroxide comprises Mg(OH)₂.
 51. The method according to claim 50where said second reaction proceeds according to a reaction mechanism ofNaBH₄+2 Mg(OH)₂→NaBO₂+2MgO+4H₂.
 52. The method according to claim 1where said hydride comprises NaBH₄ and said hydroxide comprises NaOH.53. The method according to claim 52 where said second reaction proceedsaccording to a reaction mechanism of NaBH₄+4NaOH→NaBO₂+2Na₂O+4H₂. 54.The method according to claim 1 wherein at least a portion of said wateris provided in the form of a hydrated hydroxide compound.
 55. The methodaccording to claim 54 wherein said hydrated hydroxide compound isselected from the group consisting of: hydrated lithium hydroxide(LiOH.H₂O), hydrated sodium hydroxide (NaOH.H₂O), hydrated potassiumhydroxide (KOH.H₂O), hydrated barium hydroxide (Ba(OH)₂.3H₂O), hydratedbarium hydroxide (Ba(OH)₂.H₂O), hydrated lithium aluminum hydroxide(LiAl₂(OH)₇.2H₂O), hydrated magnesium aluminum hydride(Mg₆Al₂(OH)₁₈.4H₂O), and mixtures thereof.
 56. The method according toclaim 54 wherein said hydride comprises MgH₂ and said hydroxidecomprises LiOH.H₂O.
 57. The method according to claim 54 wherein saidhydride comprises LiH and said hydroxide comprises LiOH.H₂O.
 58. Themethod according to claim 54 wherein said hydride comprises NaH and saidhydroxide comprises LiOH.H₂O.
 59. The method according to claim 54wherein said hydride comprises LiH and said hydroxide comprisesNaOH.H₂O.
 60. The method according to claim 54 wherein said hydridecomprises NaH and said hydroxide comprises NaOH.H₂O.
 61. The methodaccording to claim 54 wherein said hydride comprises LiBH₄ and saidhydroxide comprises LiOH.H₂O.
 62. The method according to claim 54wherein said hydride comprises NaBH₄ and said hydroxide comprisesNaOH.H₂O.
 63. The method according to claim 54 where in said hydroxidecomprises a non-hydrated hydroxide compound and a hydrated hydroxidecompound.
 64. The method according to claim 63 where said hydridecomprises LiBH₄ and said hydroxide comprises LiOH and LiOH.H₂O.
 65. Themethod according to claim 63 where said reaction proceeds according to areaction mechanism of LiBH₄+LiOH+LiOH.H₂O→Li₃BO₃+2 Li₂O+4H₂.
 66. Themethod according to claim 63 where said reaction proceeds according to areaction mechanism of 2 LiBH₄+LiOH+2 LiOH.H₂O→Li₄B₂O₅+LiH+7H₂.
 67. Amethod of producing hydrogen comprising: generating heat in a firstreaction by reacting water with a portion of a hydride present in afirst material composition, wherein said heat is used in a secondreaction; and reacting another portion of said hydride present in saidfirst material composition with a hydroxide present in a second materialcomposition in said second reaction, thereby forming a hydrogen productand a byproduct composition comprising an oxide.
 68. The methodaccording to claim 67 wherein said second reaction commences while saidfirst reaction is occurring.
 69. The method according to claim 67wherein said heat provides an activation energy sufficient to commencesaid second reaction.
 70. The method according to claim 67 wherein saidsecond reaction is exothermic.
 71. The method according to claim 67wherein said second reaction is endothermic.
 72. A hydrogen storagecomposition having a hydrogenated state and a dehydrogenated state: (a)in said hydrogenated state, said composition comprises a hydride and ahydrated hydroxide; and (b) in said dehydrogenated state, saidcomposition comprises an oxide.
 73. The composition of claim 72 whereinsaid hydride is represented by the formula MI^(x)H^(x), where MIrepresents one or more cationic species other than hydrogen, and x is anaverage valence state of MI.
 74. The composition of claim 72 whereinsaid hydrated hydroxide is represented by the formulaMII^(y)(OH)_(y).wH₂O, where MII represents one or more cationic speciesother than hydrogen, y is an average valence state of MII, and wrepresents the stoichiometric ratio of water in said hydrated hydroxide.75. The composition of claim 72 wherein said hydride is represented byMI^(x)H^(x) and said hydrated hydroxide is represented byMII^(y)(OH)_(y)-wH₂O, where MI and MII respectively represent said oneor more cationic species other than hydrogen, x and y represent averagevalence states of MI and MII, respectively, and w represents thestoichiometric ratio of water in said hydrated hydroxide.
 76. Thecomposition of claim 72 wherein said hydride is represented byMI^(x)H^(x) and said hydrated hydroxide is represented byMII^(y)(OH)_(y).wH₂O, where MII represents said one or more cationicspecies other than hydrogen, y represents an average valence state ofMII, and w represents a stoichiometric amount of hydrated water.
 77. Thecomposition of claim 76 wherein MI is selected from the group consistingof Al, As, B, Ba, Be, Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg,In, K, La, Li, Mg, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Si, Sm, Sn,Sr, Th, Ti, TI, V, W, Y, Yb, Zn, Zr, and mixtures thereof.
 78. Thecomposition of claim 76 wherein MII is selected from the groupconsisting of Al, As, B, Ba, Be, Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga, Gd, Ge,Hf, Hg, In, K, La, Li, Mg, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Si,Sm, Sn, Sr, Th, Ti, TI, V, W, Y, Yb, Zn, Zr, and mixtures thereof. 79.The composition of claim 76 wherein MI and MII are each elementsindependently selected from the group consisting of Al, B, Ba, Be, Ca,Cs, K, Li, Mg, Na, Rb, Si, Sr, Ti, V and mixtures thereof.
 80. Thecomposition of claim 76 wherein MI and MII are each elementsindependently selected from the group consisting of Al, B, Be, Ca, K,Li, Mg, Na, Sr, Ti, and mixtures thereof.
 81. The composition accordingto claim 72 wherein said hydrated hydrated hydroxide is selected fromthe group consisting: hydrated lithium hydroxide (LiOH H₂O), hydratedsodium hydroxide (NaOH H₂O), hydrated potassium hydroxide (KOH.H₂O),hydrated barium hydroxide (Ba(OH)₂.3H₂O), hydrated barium hydroxide(Ba(OH)₂.H₂O), hydrated lithium aluminum hydroxide (LiAl₂(OH)₇.2H₂O),hydrated magnesium aluminum hydride (Mg₆Al₂(OH)₁₈.4H₂O), and mixturesthereof.
 82. The composition of claim 72 wherein said hydride isselected from the group consisting of: lithium hydride (LiH), sodiumhydride (NaH), potassium hydride (KH), beryllium hydride (BeH₂),magnesium hydride (MgH₂), calcium hydride (CaH₂), strontium hydride(SrH₂), titanium hydride (TiH₂), aluminum hydride (AlH₃), boron hydride(BH₃), lithium borohydride (LiBH₄), sodium borohydride (NaBH₄),magnesium borohydride (Mg(BH₄)₂), calcium borohydride (Ca(BH₄)₂),lithium alanate (LiAlH₄), sodium alanate (NaAlH₄), magnesium alanate(Mg(AlH₄)₂), calcium alanate (Ca(AlH₄)₂), and mixtures thereof.
 83. Thecomposition of claim 72 wherein said hydride comprises MgH₂ and saidhydrated hydroxide comprises LiOH.H₂O.
 84. The composition of claim 72wherein said hydride comprises LiH and said hydrated hydroxide comprisesLiOH.H₂O.
 85. The composition of claim 72 wherein said hydride comprisesNaH and said hydrated hydroxide comprises LiOH.H₂O.
 86. The compositionof claim 72 wherein said hydride comprises LiH and said hydratedhydroxide comprises NaOH.H₂O.
 87. The composition of claim 72 whereinsaid hydride comprises NaH and said hydrated hydroxide comprisesNaOH.H₂O.
 88. The composition of claim 72 wherein said hydride comprisesLiBH₄ and said hydrated hydroxide comprises LiOH.H₂O.
 89. Thecomposition of claim 72 wherein said hydride comprises NaBH₄ and saidhydrated hydroxide comprises NaOH.H₂O.